The legislature chose instead to endorse "civil unions" - which gives gay people similar rights to married couples but denies them the title of marriage. "It's terribly wrong to think that God would be pleased," said one man. "If we recognise gay marriage there will be more attacks on this country, chemical, biological, terrorist."

About 800 miles away, in Spartanburg, South Carolina, the first batch of an evangelist, apocalyptic bestselling novel, The Glorious Appearing, has just arrived in the Christian Supply store. The 12th book in a series offering a modern-day rendition of the Book of Revelation, in which the antichrist is the head of the United Nations, has sold more books than John Grisham. Around 800 people queued to get their books signed on Tuesday.

Back in New York, Wednesday saw comedian Al Franken open a new, liberal talk radio station, Air America, with the following message: "This show is about taking back our country. It's about relentlessly hammering away at the Bush administration until they crack and crumble this November. Our friends on the right - and they are our friends ... except for the ones who aren't - say that we liberals are angry. Yeah. Yeah, we're angry."

Welcome to the culture wars - the daily indicators that the polarisation in US politics has both spawned and is being fed by a huge cultural rift that extends from the airwaves to the altar and from the bookshelves to the bedroom. Alongside concrete issues like the economy, the war and healthcare, a bitter battle has emerged over individual lifestyle and moral values, oscillating between the personal, racial, social, sexual and religious, which is shaping the battleground for the forthcoming election.

This is not new to American politics. When the Democrats ran a Catholic, Alfred Smith, for president in the prohibition era of 1928, Republicans raised the threat of "Rum, Romanism and Ruin". In 1968, as feminism, black power, free love and the anti-Vietnam war movement gathered pace, Richard Nixon pledged his support for "the forgotten Americans, the non-shouters, the non-demonstrators. Good people who work, save, pay their taxes and care".

But this time around it seems particularly intense. The nature of the conflict is ill-tempered and ill-defined, ranging from the outrage over the flash of Janet Jackson's breast during the Superbowl's half-time entertainment, to the supreme court challenge to the term "one nation under God" that all children recite every day in schools. But the outcome is specific and crucial. In an election as close as this promises to be, whoever wins the culture wars - or is perceived to win - is likely to win the presidency.

It has seen not only the injection of cultural issues into politics, but also, increasingly, the politicisation of culture too. When a George Bush lookalike asks to use the toilet in Whoopi Goldberg's sitcom, Whoopi, she says: "I can't believe he's in there doing to my bathroom what he's done to the economy." In November, CBS pulled a mini-series about Ronald and Nancy Reagan after pressure from conservatives, who threatened to launch an advertising boycott because it was too critical.

In many ways, the two presidential candidates present a distinct cultural choice. True, both Bush and Democrat John Kerry are privileged, white, male, blue-blooded Ivy League graduates with roots in old money. But Bush is a former frat boy who wears cowboy boots and whose favourite philosopher is Jesus; Kerry has wavy hair, a foreign wife and enjoys reading and writing poetry.

All of this is as trite as it is significant. Presidential elections are not just determined by who has the best policies but which candidate the American people feel most comfortable with as a person. The Republicans are trying to brand Kerry a Massachusetts liberal, while the Democrats are keen to depict Bush as a rightwing, Texan cowboy - such insults are as cultural as they are political.

At the core of this struggle lies longstanding tension between religiosity and modernity that makes the US exceptional among western nations. In no other country with America's wealth and constitutional guarantees of individual liberty and regional autonomy does religion play such a central role, with 86% of people believing in miracles, 89% believing in heaven and 73% believing in the devil and hell.

As a result, the culture wars are not just about competing world views of people who read different books and watch different films. They are waged by people who, for the most part, occupy entirely different worlds. This is true not only culturally but geographically too. Broadly speaking, along with a handful of cities like Chicago, the coasts to the west and northeast are predominantly liberal, while the huge swath of the rural Midwest, Great Plains and mountain states in between are overwhelmingly conservative. The result is a dislocated and at times dysfunctional national political culture, where people share a political and cultural space (everyone gets to vote for the president and watch network television) but few common reference points in their daily lives.

For the most part, this is America's strength - to contain and harness the diversity this brings - but at certain points, such as the civil war or the civil rights era, it can exert a great strain.

Nowhere is this more obvious than in the row over homosexuality in general and gay marriage in particular. Polls show Americans are divided as a nation and conflicted within themselves. Most believe in equality for gays, but still want to deny them the equal right to marriage, while supporting civil unions.

The president has vowed to change the US constitution to make marriage an exclusively heterosexual affair, and some states, like Massachusetts, have voted to do the same. Other towns and cities, including San Francisco, have been issuing marriage licences to same-sex couples. Corvallis, a small town in Oregon, has refused to marry anybody until the matter is cleared up. Meanwhile, the hit reality show of last year was Queer Eye for the Straight Guy, in which five gay men makeover a straight man for a special occasion, and one of the most popular sitcoms is Will and Grace, about a gay man and his female friend.

Such a fractured and uneven cultural landscape makes for unpredictable politics, where deep-seated prejudice is weighed up against other strongly held allegiances. Polls show African Americans are just as hostile to gay rights as whites but are still likely to vote Democrat in large numbers. When the author Molly Ivins asked a civil liberties activist from Midland, Texas, whether there was much of a problem with gay bashing in the area, the woman replied: "Hell honey, there's not a gay in Midland who would come out of the closet for fear that people would think they're a Democrat."